Mass storage devices such as hard disk drives are many times the slowest link in an operational computer system. As hard disk drive access latency gets worse, total computer system performance generally declines because the fast processor and memory in the computer system have to frequently sit idle waiting for the disk drive to provide access to data. Thus, any type of performance improvement in hard disk input/output (I/O) may provide an overall improvement of the performance of the computer system as a whole.
Disk drives have historically utilized ATA (Advanced Technology Attachment)-type commands. Recently, a new set of commands were introduced for serial ATA (SATA) hard disk drives using the AHCI (Advanced Host Controller Interface) called native command queueing (NCQ). NCQ-type commands were designed to increase performance in dealing with large bursts of disk access requests. Though burst performance may have improved, NCQ-type commands do not tend to perform well when access requests trickle in one at a time or arrive together in low numbers.